1. Field of the Invention
The present invention relates in general to a radio-telephone system having a stationary apparatus and a portable apparatus, for intercommunication between the both apparatus by wireless and a method of performing the intercommunication between the both apparatus by wireless, and more particularly to a radio-telephone system employing a manner of changing a channel and a privacy digital code and interstoring them between the both apparatus by wireless, for transmitting the privacy digital code from the stationary apparatus to the portable apparatus through their antennas by wireless and storing the privacy digital code into a RAM in the portable apparatus, when the portable apparatus is put on the stationary apparatus for the charging of its battery and a method of changing the privacy digital code.
2. Description of the Prior Art
Generally, a radio-telephone system having a stationary apparatus and a portable apparatus is believed to hold a privacy digital code in order to prevent an unlawful use thereof and a misconnection between the both apparatus.
In a conventional channel-fixed radio-telephone system, there has not been present any alternative plan to a severe crosstalk in the course of a talker's talking over the telephone. Also, the system could not solve the problems of misconnection between the both apparatus in the talker's trying to talk over the telephone because of its holding no privacy digital code, and therefore of the overcharge for the telephone call.
Also, there has been known another conventional radio-telephone system provided with Manchester Code, encoder/decoder chips for embodying the holding of the privacy digital code in the operation of dip switches corresponding to a predetermined number of digital code bits. In this system, however, the change of the digital codes was allowed very restrictively in view of economic conditions for a system hardware and of the number of digital code bits and, as well, the dip switches for the stationary and portable apparatus was inconvenient to use due to their manual operations.
Conventional radio-telephone systems adopted for the improvement in the above-mentioned problems with above systems will be mentioned hereinafter with reference to FIGS. 1 and 2.
Referring to FIG. 1 which is a block diagram of a construction of a conventional radio-telephone system issued to MOTOROLA Co., Ltd, U.S.A., this conventional radio-telephone system is shown to comprise a stationary apparatus and a portable apparatus each including a microprocessor, a memory, two (+,-) charging terminals and a separate coding terminal ID. This system is adapted to send a predetermined privacy digital code from the stationary apparatus out to the portable apparatus via the coding terminal ID and then store it into the memory in the portable apparatus, when the predetermined privacy digital code is previously programmed in the memory in the stationary apparatus and the portable apparatus is thereafter put on the stationary apparatus for the charging of its battery.
Turning to FIG. 2 which is a block diagram of a construction of another conventional radio-telephone system issued to AT&T Co., Ltd, U.S.A., this conventional radio-telephone system is shown to comprise a stationary apparatus and a portable apparatus, each including a control circuit containing a memory, two (+,-) charging terminals and a charging, data transfer and cradle status circuit connected between the control circuit and the two charging terminals, with removing the separate coding terminal ID from the above-mentioned system. This system is adapted to send a predetermined privacy digital code from the stationary apparatus out to the portable apparatus via the (+) charging terminals, not via the coding terminal ID in the above-mentioned conventional system and then store it into the memory in the portable apparatus, when the predetermined digital code is previously programmed in the memory in the stationary apparatus and the portable apparatus is thereafter put on the stationary apparatus for the charging of its battery.
However, in the former system, the installation of the separate coding terminal therein results in its structural complexity and in the latter system, the additional installation of the charging, data transfer and cradle status circuit therein results in its structural complexity and a heavy economic burden thereof. In addition, in both systems, the use of expensive EEPROMs in which each of equally programmed privacy digital codes is stored, in both of the stationary and portable apparatus results in an increase in the economic burden thereof.